The present invention relates to a process for manufacturing heat sinks which are to be used for semiconductor devices or like heat generating articles as attached to the heat sink or to be attached to electronic devices having a heat generating article incorporated therein for dissipating the heat generated by the article.
The term xe2x80x9caluminumxe2x80x9d as used herein and in the appended claims includes pure aluminum, commercial aluminum containing traces of impurities and aluminum alloys.
Heat sinks are already known which comprise a multiplicity of tonguelike fins formed on the upper surface of a heat dissipating base plate. The base plate of the heat sink has holes, such as threaded holes, holes for driving tapping screws thereinto and bolt insertion holes, for use in attaching the article to be cooled to the base plate or attaching the heat sink itself to the device to be cooled by radiation. Although burrs are produced when the base plate is drilled, the multiplicity of tonguelike fins on the upper surface of the heat dissipating base plate present difficulty in removing the burrs completely, necessitating labor and time for deburring.
An object of the present invention is to provide a heat sink having a heat dissipating base plate in which blind holes not extending to the upper surface of the plate can be formed so as to obviate the problem with the burrs.
The present invention provides a process for manufacturing a heat sink comprising a heat dissipating base plate and a multiplicity of tonguelike fins formed on an upper surface of the base plate. In this process, a heat sink blank of aluminum extrudate is formed first which has a part for forming a thick portion of the base plate, a fin forming portion provided on an upper side of the thick portion forming part integrally therewith, a thin portion of the base plate provided at at least one of opposite sides of the thick portion forming part, and a level reference ridge formed on an upper surface of the thin portion and having an upper end at the same level as an upper surface of the thick portion to be formed. The fin forming portion of the blank is cut to raised form at the same level as the level of the upper end of the reference ridge to form a multiplicity of tonguelike fins and form a thick portion of predetermined thickness under the fins. This assures the thick portion of the accuracy of its thickness. Further if the fin forming portion of the heat sink blank is cut to excess to partly cut even the thick portion forming part beneath the fin forming portion to give the thick portion of the heat dissipating base plate a smaller thickness than the specified value, the upper portion of the level reference ridge is also cut to a raised form. This cut portion therefore readily indicates that the product is faulty.